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In-Situ Measurement of Soil Moisture at the KUREX-91 Streletskaya Steppe Sites

机译：KUREX-91 Streletskaya草原站点的土壤水分原位测量

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Measurements were obtained at Kursk Biospheric Reserve Station (BRS) throughout the period from 6 July through 27 July, 1991. Both gravimetric and dielectric measurements were obtained daily for all sites on the steppe. Soil sampling points were selected near each corner of the three sites (i.e. southeast, southwest, northwest, and northeast field corners). This scheme was slightly modified for the primary site, field 12, to achieve better coincidence with Soviet measurements. The moisture content of the top 10 cm of soil was examined by extracting a cylindrical core approximately 2 cm in diameter and 10 cm long at four sampling locations in each of the three test sites/fields. Two cores were extracted from each sampling location and combined in a single sampling container for subsequent gravimetric analysis. These samples were weighed in the laboratory several hours after being obtained and placed in drying ovens at a temperature of 110℃ for approximately 48 h. Dry weights were then obtained and the original soil moisture content calculated. The complex electrical impedance at 10 MHz was measured to determine the dielectric properties of a cylindrical volume of soil contained within a specially designed probe. Probes were placed in the southeast corners of each site at depths of 5, 10, and 20 cm. These probes were collocated with Soviet neutron activation tubes at the southeast sampling location for each of the three test sites. Additional sets of probes were placed at the other three sampling locations in the primary test area (site 12). These probes were placed at 5, 10, and 20 cm for the northwest and northeast sampling locations. An even more elaborate scheme was employed at the site 12 southwest location in the vicinity of the Fritchen flux measurement station. Six probes were placed as follows: two at 5cm, one at 10cm, one at 15cm, and two at 20cm. The dielectric properties of soil are strongly dependent on the moisture content since the dielectric constant of pure water is almost two magnitudes greater than that of soil containing no free water. Therefore the probe measurements were combined with the gravimetric measurements to produce estimated daily soil moisture profiles from the surface to 20cm depth for each of the three steppe sites. The within field variability was also estimated for each site on a daily basis. These estimates are shown to be consistent with vegetation cover and precipitation history.
机译：在1991年7月6日至7月27日的整个期间，在库尔斯克生物圈保护区（BRS）进行了测量。每天对草原上的所有地点进行重量和介电测量。在这三个地点的每个角落（即东南，西南，西北和东北田间角落）附近选择土壤采样点。对于主要站点（字段12），对该方案进行了稍微修改，以实现与苏联测量的更好的重合。通过在三个测试点/区域中的每个采样点的四个采样位置提取直径约为2 cm，长度为10 cm的圆柱状芯，检查土壤顶部10 cm的水分含量。从每个采样位置提取两个岩心，并合并在一个采样容器中，以进行随后的重量分析。这些样品在获得后的几个小时内要在实验室称重，然后在110℃的干燥箱中放置约48小时。然后获得干重，并计算原始土壤水分含量。测量了10 MHz时的复电阻抗，以确定包含在特殊设计的探头中的圆柱形土壤的介电性能。将探针放置在每个站点的东南角，深度分别为5、10和20厘米。这些探针与苏联中子活化管在三个采样点的东南采样位置并置。在主要测试区域（站点12）的其他三个采样位置放置了另外的探针组。这些探针分别放置在西北和东北采样位置的5、10和20厘米处。在Fritchen通量测量站附近的西南12号站点采用了更为精细的方案。如下放置六个探针：两个在5厘米处，一个在10厘米处，一个在15厘米处，两个在20厘米处。土壤的介电特性在很大程度上取决于水分含量，因为纯净水的介电常数比不含自由水的土壤的介电常数大两个数量级。因此，将探针测量结果与重量测量结果结合起来，可以得出三个大草原每个地点从地表到20厘米深度的估计日土壤水分剖面。每天还估算每个站点的场内变异性。这些估计值与植被覆盖和降水历史一致。

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